lost address book after upgrading to thunderbird 102.7.1

You don't need to ask twice. What was the prior version?

I did not check the existing version before I upgraded to 102.7.1

You might check to see whether there is an abook.mab or abook.sqlite somewhere on your PC. If so, you can use tools>import>import from a file.

Both of those files exist in the Profile folder in AppData as well as History.mab and History.sqlite.

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